The present invention relates to a polishing composition for use, for example, in polishing for forming conductive wiring in a semiconductor device, and a polishing method using such a polishing composition.
Conductive wiring in a semiconductor device is at present mainly produced by a damascene process, which is based on a chemical mechanical polishing (CMP) technique. For producing conductive wiring, trenches are first formed on an insulating layer of insulating material (e.g., SiO2), provided on a semiconductor board. Next, a conductive layer of conductive metal (e.g., Cu) is provided on the insulating layer so as to at least fill up the trenches. Then, the portion of the conductive layer, which is positioned outside the trenches, is removed by polishing. As a result, the portion of the conductive layer, which is positioned in the trenches, remains on the insulating layer acts as conductive wiring.
Polishing for removing the portion of the conductive layer, which is positioned outside the trenches, is generally carried out with a polishing composition that contains an abrasive grain, an oxidant, and an agent for forming a protective film. The polishing compositions disclosed in International Publication No. WO00/13217, Japanese Laid-Open Patent Publication No. 8-83780, and Japanese Laid-Open Patent Publication No. 11-21546 contain an agent for forming a protective film, including a nitrogen compound such as ammonia, benzotriazole and a surfactant. The polishing composition disclosed in Japanese Laid-Open Patent Publication No. 7-233485 contains an organic acid such as aminoacetic acid, and an oxidant.
CMP for removing the portion of the conductive layer, which is positioned outside the trenches, is generally carried out in two stages to enhance efficiency, i.e., a preliminary polishing step for polishing a subject to be polished with a high stock removal rate and a finish polishing step for finish-polishing the subject to be polished so that a favorable surface qualities can be obtained. The preliminary polishing step using a polishing composition for the preliminary polishing step and the finish polishing step using a polishing composition for the finish polishing step are generally continuously carried out using a single polishing machine equipped with a plurality of polishing turntables. Therefore, the polishing composition for the finish polishing step may be left adhere to the polishing machine and the remained polishing composition for the finish polishing step may mixed into the polishing composition for the preliminary polishing step in the subsequent polishing cycle. Some polishing compositions for the finish polishing step contain an agent for forming a protective film such as benzotriazole or polyvinyl pyrrolidone. When the polishing composition for the finish polishing step is mixed into the polishing composition for the preliminary polishing step, a protective film is formed on the conductive layer by the action of the agent for forming a protective film in the polishing composition for the finish polishing step, causing a significant deterioration in the stock removal rate in the preliminary polishing step. Moreover, since the amount of contamination varies from cycle to cycle, and the degree of deterioration in the stock removal rate in the preliminary polishing step fluctuates from cycle to cycle, causing a variant stock removal rate in the preliminary polishing.